


Symbiotic

by FullElven



Category: Supernatural
Genre: Addiction, Alcoholism, Blood Drinking, Cutting, M/M, Sexual Situations, slight dub-con
Language: English
Status: In-Progress
Published: 2014-05-23
Updated: 2014-05-24
Packaged: 2018-01-26 06:59:02
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 2
Words: 4,064
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1678982
Author URL: https://archiveofourown.org/users/FullElven/pseuds/FullElven
Summary: <blockquote class="userstuff">
              <p>Dean isn't the breed of demon that can make demon deals, but he realizes that he can prolong a life if he lets someone drink his blood. Knowing this, he sets out to convince Castiel to do just this, knowing he'll live if he does, even if his stolen grace fizzles. The exchange, however, seems to have unforeseen consequences.</p>
            </blockquote>





	1. Not That Kind of Demon

“I know you’re there Dean, I can smell the sulfur,” Cas spoke in a near monotone voice, standing on the edge of the outlook that peered over the smaller Midwestern town. Saint Joseph, Missouri he believed it was, but to tell the truth, they all just seemed to look the same to him.

There was an audible sign behind the angel and within a blink, Dean Winchester appeared. His black eyes quickly faded to green, a little saddened, but otherwise focused on the trenchcoat clad back of Castiel. “How did you know it was me, and not some other demon.”

Just the barest hint of blue was visible as he glanced back over his shoulder toward Dean, the silver moonlight making the demon’s skin look pale. “The sulfur doesn’t cover the scent of your leather jacket.”

“Yeah, well…” Dean was at a loss for words, looking away from Cas for a long moment. “Thought you were working a case. Where’s Sammy?”

“Drinking at the hotel with some woman.” There was no trace of annoyance in the angel’s tone, stating it as if it were a statistical fact. “I didn’t wish to wait to see if it progressed where I thought it was headed.”  
  
The gravel crunched beneath black biker boots, boots he still stubbornly wore beneath the black three-piece suit he donned most stays now. Fingers gripping the cool railing protecting viewers from going over the edge of the overlook, Dean looked over the pathetic little town of 75,000 and sighed. “Your grace is almost gone. It’s not so bright that it burns my eyes when I look at you now.”

For a long moment, Cas didn’t comment. A stiff wind whipped by, catching the large American flag above their heads and causing the small dingy rope used to lower and raise it to slap against the metal pole. “I can no longer see your true face.” Castiel admitted at last. “I think this is why Sam drinks. It won’t be long before he has lost us both.”

“Well, if he wasn’t so damned stubborn and realize that I’m still the same ol’ Dean, maybe he wouldn’t be alone.” He practically growled for his irritation at how pigheaded his younger brother was being, and Cas tossed a glance his way, just looking all the more sad for it. Dean dropped it in favor for the issue at hand. “Your grace was the reason that I was looking for you.”

“I’m not making a deal, Dean. This is my punishment, I am prepared to die.”

“Stop talking like that.” He demanded. “And I can’t make deals, not that flavor demon.” Turning to lean his forearm against the railing so that he could watch Cas, he locked those vividly green eyes on him. For once, Castiel thought he knew what it was like finally to be the one being stared through to their core. “I was reading something in one of Crowley’s texts—“

“I’m not interested in anything he has.” Cas interrupted, and Dean groaned.   
  
“Stop acting like Sammy, and hear me out will ya? My blood can save you, I’m pretty sure of it. You saved my bacon how many times, Cas? Let me bleed a little for you. It’s the least I can do.”  
  
Those brows furrowed and Cas closed the distance between them, standing well within that personal space bubble on purpose, looking up into the eyes of Dean Winchester the demon. “If it weren’t for  _me_ , you wouldn’t even have demon blood.”

“Damn it, Cas, I’m serious.”  
  
“As am I, Dean.”   
  
“Fine, if you think you’re responsible, then you owe me. And I want you to pay me back by not dying. Drink a little from the tap, live a little longer, put a smile on my face.”

The angel looked entirely offended at Dean’s twisting the situation around like that, and started to move away from him. “That’s the demon in you talking, Dean.” The demon’s hand darted out to catch Cas’s wrist in a powerful grasp, spinning him around until he was chest to chest with him almost, and Castiel was forced to look up into the black eyes of that  _demon_.

“The demon in me would just as soon feel  _your_  blood seeping into my pores.  _I_ , want you alive and well. Or did you forget that we were friends once?”

Cas couldn’t stare into that vast blackness, not without guilt and sadness threatening to drown him, and he adverted his gaze. Dean caught his chin though between a thumb and forefinger and made him look back up at him, shocked blue eyes finding his now green ones again as the slightest hint of color found the angel’s cheeks. “Trust me, Cas. I’m not going to steer you wrong. As much as you and Sam want to believe that I’m the bad guy here, I just want to help. Meg wanted to help once upon a time, and you were alright with that.”  
  
Silence followed, but Dean could see the wheels turning in his head, practically hear the sound of his own victory as Cas realized that he was not wrong in that. “I don’t like the taste of blood,” he protested weakly, but the demon could see his angel had already decided to give in.

“It’s not so bad once you get used to it. Come on,” Dean motioned with his head toward Cas’s old beater. “Probably shouldn’t do this in the open.”

The angel didn’t resist him, and instead let him pull him in the direction of his automobile, each step making his invisible wings feel heavier and heavier, as if they were more burden than appendage. He opened his door though and sank into his bench seat, leaning to unlock Dean’s door before he closed his own.

Dean unbuttoned his well-tailored suit jacket and leaned to toss it in the backseat before he slid in himself, closing his door and working on his cuff link next. The button slipped through the fabric easy, and he was able to peel the fabric back and expose his forearm. Cas seemed to look everywhere but at him, unable to stop moving as the nerves ate at him. “This isn’t right,” he said quietly. Dean quietly shhhh’d him as he opened his hand, a small two in blade not more than a pocket knife really appeared in his hand.

“C’mere.” He scooted a little toward Cas, but ultimately he meant for him to meet him halfway. The angel did, and he smiled more for the submission. He wanted him to do it of his own volition, to make his own choice to let him save him. “If you don’t want this, you tell me, and I’m out. Out of here, out of your life, I’ll leave you alone. No fine print.”

Cas looked up at him again finally, and Dean could see the fear in his eyes before he shook his head. “I…I don’t want you to leave. I don’t wish to die.”

Taking that as permission, Dean pressed the sharp blade to his flesh, the metal of it glinting in the moonlight. He pulled it across his flesh, and the way he set his jaw, closed his eyes, and let his head fall back a little…Cas couldn’t tell if it hurt him or if it pleasured him. “Here.” He moved his arm a little for emphasis and Castiel wrapped his warm, sweating palms around his forearm to pull it to his face.

Dean could feel the scruff of his face like sandpaper against the sensitive area of that cut, the tentative drag of his wet tongue along the length of it, causing the wound to sting. Cas had his eyes closed, but Dean’s darkened to black as a sudden and unexpected rush of warmth ignited in the pit of his stomach. He could feel that initial hesitance to taste him more, but slowly it melted until Cas’s lips parted more around it and he sucked lightly, tonguing at it when the blood seemed to slow a little.  
  
It wasn’t a sexual act, the demon reminded himself, even as he felt himself stir in his trousers. This was  _Cas_ , and while yeah, he’d always thought he was good looking and was fonder of his company than lent to being entirely straight, he had tried not to think of him like  _that_. But with him attached to his arm, suckling, tasting, and… _God was that a groan?_  Dean found his breath coming quicker, his pants becoming uncomfortable, and his skin warming.

“ _Jesus_ , Cas.” He groaned inadvertently, stretching a leg out and trying to give himself some room down there.

Cas pulled off, his own breath coming faster, and Dean could see his blood smeared across his lips, a little on his chin, and he twitched for the beautiful fantasies that filled his mind. Cas’s eyes were but a slivered ring of blue around the edge of black pupil. “Am I hurting you?” His gruff voice sounded deeper. 

“Yes, but I’m not saying stop, am I?”

Cas did stop though, looking a little sheepish as he leaned back in the seat, letting his head rest against the headrest as he breathed deep, licking his lips, hands rubbing the skin of his arms in a sensual motion. “I could taste  _you_ ,” he said, his voice just a whisper now. “It makes my skin buzz. There’s so much…energy.”

Dean didn’t complain as Cas laid a little closer to him, even as he swallowed hard. This wasn’t how he’d planned this. “Yeah,” cough. “Heard it might be a bit of a headrush.”  
  
“I feel like you’re a part of me.” He continued, laying his head on Dean’s shoulder with absolutely no regard for personal space. Reaching his hand out toward nothing, he wiggled his fingers, grasped the air. “There’s nothing like this, Dean.”  
  
As amusing as getting an angel high on demon blood seemed at first, Dean found himself entirely distracted with just how arousing the whole thing had been for him. “Yeah, well. We uh…we have to do this um…” Words were hard to come by, his head clouded in a pleasant fog that seemed to only part for indecent thoughts of his friend. “Once a week. I can come to you…when I know for sure you’re uh…alone. Sammy won’t be happy about this.”

Cas didn’t say anything.

Unable to turn his head to look at him for how he laid on him, Dean moved the rearview mirror until he could see here. Castiel was fast asleep already on his shoulder, and the demon mused on how it likely would be the only time he ever had a little angel on his shoulder again.


	2. Awakening

**Summary for the Chapter:**

> Dean isn't the breed of demon that can make demon deals, but he realizes that he can prolong a life if he lets someone drink his blood. Knowing this, he sets out to convince Castiel to do just this, knowing he'll live if he does, even if his stolen grace fizzles. The exchange, however, seems to have unforeseen consequences.

Castiel awoke to all too bright sunlight drifting in through his car window, spittle soaking the side of his face and the seat of the car. His memory was a haze in those first few waking moments, but as he sat up, he caught a hint of leather and sulfur, immediately turning where he sat.  
  
Only to find no Dean Winchester.

He did spy the jacket of his suit still tossed in the backseat, the only remnant left to remind him that the other night had not been a dream. Well, that was, until he moved to fix his rearview mirror and found the area around his mouth crusted with dark blood. For a moment, shame loomed on the outer fringes of his emotions, threatening to take him over. He _wanted_ to feel ashamed and maybe even mad at himself, but he found the longer he focused on it, the less he could even feel it. Like sand slipping through loose fingers, it refused to stay with him.  
  
By the time he’d reached the hotel, he found that not only was he alright with it, but he really, really missed Dean. It had been the first time in a while that things had felt alright. When he’d found out he was alive, he couldn’t get to his side fast enough. But when he’d arrived, when he’d seen what that grotesque demon essence had done to his once beautiful soul, he’d felt broken. Defeated. When Sam had turned Dean away, Cas couldn’t even look at him and had done his best to avoid him for weeks.

Not because of Dean…but because of what he fully believed he’d _done_ to Dean.

And yet, after over a month of being out of their lives, even after everything, Dean was still trying to save Cas’ life…it was a hard thing for the angel to wrap his head around. It’s also something that made him love that human…er _demon_ …more.

It was that love that kept his mouth shut as he and Sam finished the St. Joseph job, putting down a demon who seemed far more interested in wrecking young woman and quoting pop culture than to realize its imminent demise, that they headed up north toward Bellevue, Nebraska where rumors of a supposed haunting had been making the news for the past couple days.

Cas drove, letting Sam sleep off his hang over along the two and some change hour drive. He hadn’t slept long himself, and the rolling plains and fields full of nothing made it hard for him to keep his attention on the road ahead of him. The lines threatened to swim as his mind wandered to the feel of Dean’s warmth against the side of his body, the way it felt to take in his tainted blood, the feeling as if what was left of Dean’s tattered soul swam inside _him._

It had been such an incredibly intimate exchange, enough of one that it hadn’t been missed on the sometimes naïve angel, but he wondered just what was in it for Dean. That talk of doing it for _him,_ of living _for him_. Castiel was not blind to the numerous female relationships that he’d had pre-demon turning, and being a demon now, he had a hard time believing that Dean was doing it from the goodness of his heart.  
  
For all of Meg’s affections, she’d always had something to gain from her kindness to him.

The difference, he found surprisingly, was that part of him was fine with the idea of Dean using him if it meant that he’d at least get to see him once a week. “That’s not healthy at all.” He murmured, straightening the car before he could find himself drifting over onto the annoyingly textured shoulder. Sam didn’t even budge from where he snored, long legs looking cramped as ever in the cabin.

This time, Cas got them separate rooms, something that Sam didn’t even have it in him to protest as he grabbed his gear and disappeared to presumably find the minibar. Castiel worried after him, but got nothing but the solid closing of oak door in his face for his trouble. With a heavy sigh, the angel unlocked his own door, pushing it open with his foot, and letting it fall closed behind him.

“’Bout time.”

Castiel nearly jumped right out of that worn old trench coat at the sudden voice, only eliciting a dark chuckle from the owner of it. “Hah, payback’s a bitch, isn’t it?”

“Dean…”

“Miss me, beautiful?”

Castiel’s cheeks colored pink, and he coughed nervously, not looking in his direction. “It’s only been seven days,” he covered, trying to play it cool. There was an unusual waver to his usual timbre, and Dean canted his head from where he sat on the kitchen counter watching him.

He said nothing, and Cas confused by the sudden silence, turned finally only to find that he hadn’t left. No, Dean Winchester was right there, and looking good enough that he could feel that blush on his cheeks deepening beneath his scruff. He sat there, legs apart, bracing himself with one palm on a thigh, the other on his chin as it was supported with this elbow on his opposite thigh. Just posed there, watching him. He wore those biker boots again, the dress pants, but this time his black shirt was without tie and the first couple buttons undone to reveal the smooth skin below.

Castiel was staring, and Dean couldn’t help but to smile knowingly. “Seven _long_ days,” he said, drawing out ‘long’ as if it’d been torturously so. “How are you feeling?”

How was he…the angel had to reign his mind back in and actually _think_ about it. They’d been so busy, and he’d been so preoccupied with what had happened between he and Dean, he hadn’t actually paused to wonder if his attempt had worked. “I…feel better. I think. I have not been as tired.”

“Good. Good, means it’s working then.” Dean rubbed at his clean shaven cheek, staring through Castiel as if he were both concocting a nefarious plan and finding the answers of the universe in his dwindling grace. “You know, though, that this won’t keep your grace from running out, right? I can save you, but I don’t have the juice to be putting any angel mojo back in you.”  
  
It was hot in there, wasn’t it? The angel was sure of it, and peeled out of his trench coat and suit jacket, undoing his backward tie. “Will I become a demon?” It was an important thing to know, if not just a little late in asking this far in the game.

Dean shrugged. “Would it be so bad?”

Cas looked down and away, eyes moving as he worked out the pros and cons of it. “I suppose it wouldn’t. There doesn’t seem to be anything wrong with you.” Aside from eternal damnation and the strong smell of sulfur.

Dean’s laugh at his reply was rich, resonating deep in his chest. How could such a Heavenly sound come from something swaddled in darkness? “Well, I hope not. Seems like I’m in this for the long haul.” There was something in the way his smile didn’t reach his eyes that made Cas think that perhaps…perhaps Dean wasn’t as happy being a demon as he thought.  
  
“You miss Sam.” The words left his mouth as soon as he thought them, and what bit of that false smile had existed vanished entirely.  
  
“Yeah, well…whatever. He’s being a bitch. Not even demon blood can fix that.”

Sliding from the counter top, the thick souls of his shoes thudded dully on the faded cheap linoleum. “Perhaps you could talk to him. His drinking is unhealthy, and he has become distant.”

“I don’t want to talk about it, Cas, alright?!” The outburst made him jump, his invisible wings flapping hard once, and had the angel had enough grace, he likely would have disappeared in that instant.

Those now black eyes stared at him for a long moment, undoubtedly seeing the reaction with that true sight of theirs, before Dean was able to blink them away. “I’m here for you, not for him,” he said a bit quieter then, crossing to the minibar and fishing out a mini bottle of Jack Daniels. “I can’t fix everything.”

Cas sighed, fingers gripping the back of a chair, one sinking through a hole and into the yellowed padding. Dean uncapped his alcohol and drained the tiny bottle in one go. “Damn demon blood makes getting drunk a feat of strength.”

He glanced at Cas from the corner of his eyes, just in time to catch a small grin. His dead heart felt as if it fluttered a ghost of a second, and he breathed sharply in surprise for the sensation. Clearing his throat, he took himself over to the lumpy old bed and threw himself down on it, flipping on the television. A baseball game was already six innings in with two teams he cared nothing about, and he let the sound of the announcers fade into indiscriminate background noise.

“So…we gonna do this?”

The angel turned to look at him, pink cheeked, staring at him laying sprawled out on the bed and entirely confused as his intentions behind the words for the moment. “What?”  
  
“You gonna come drink this or am I going to bleed myself into a cup for you to put up for later? I take it you and Sammy ain’t starting on this case tonight?”

“It isn’t likely, no.”

Dean patted the bed beside him in answer to that then, and propped himself up against the headboard. Cas’s feet moved without any coaxing from his brain, pulling him closer to the bed, while Dean brandished a knife from his pocket this time, and flipped it open. He waited until Cas had planted his ass, moving closer to him before he started to slide. “Try not to bleed on my bed.”  
  
“You better not waste it, then.”  
  
This time as Dean cut, Cas knew he heard an unmistakable groan from him, and not at all an unpleasant pained one. The angel wasted no time in attaching himself far more eagerly to his arm this time around. Copper coated his tongue, mixed with something bitter, but there it was again…that tell-tale taste of _Dean_. It was indescribable.

Dean watched Castiel suckle at his arm, feeling that familiar heat settle, the stirring below. He mentally had to still his hips to keep them from moving slightly in rhythm to his sucking.

And then the angel turned his head slightly, pupils dilated, and smiled a bloody smile against his arm, watching him as he ran the tip of his tongue along the deep cut. A shiver shot through Dean’s spine like a flash of lightning, and he couldn’t keep from the quiet moan that left his lips. Cas’ eyes half closed and they fluttered behind their lids.

“Here, here, hold on.” Dean voice coaxed, barely audible. He had to pull his arm from Castiel before he took his knife and made another slit, his hand clutched in a fist as he did so. Warm crimson poured forward quickly, and Cas was on it immediately. “Lay back.” Cradling the back of the angel’s head with his palm, he helped him move until he was laying flat in that bed, Dean on his side.

Timidly, the demon ran his fingers through that messy brown hair, and he could feel Castiel’s arm breath against the skin of his arm as he groaned softly. “ _Fuck, Cas_.” He wasn’t sure how much longer he was going to last out, the electricity on the air palpable. Dean’s fingers gripped the angel’s hair and in response, Cas bit him lightly.

That was it, Dean came undone, and pulling his arm from his grasp, he leaned to replace it with his lips in a powerful kiss. His fingers still buried in Castiel’s hair, he devoured him, his tongue tasting and the angel not even thinking twice as he returned it. That Dean could taste himself on Cas’ tongue just drove him while and he found himself unable to keep from grinding against his leg.

It wasn’t until he felt his hand resting against his chest where his heart no longer beat that Dean surfaced, blood smeared on his lips. Looking down at where Cas’s hand rested was jarring, such a simple and potentially meaningless act piercing him to his very core. His heart no longer beat, no matter how badly he wished it could, that he wished he could give Cas some confirmation that it would beat for him.  
  
Suddenly, Dean was very, _very_ aware of just how far he’d fallen.  
  
Castiel didn’t seem to mind, trying to go for the kiss again. “No. Cas….we…I can’t. Y-you’re not thinking right. You’re high as a kite.”  
  
“I need you, Dean,” he begged, grabbing a fistful of that black button up shirt. Dean looked away, black eyed, but the emotion in them no less true. It killed him, his eyes tearing up to see how desperate the angel clung to him. What was he doing to him?

“You don’t know what you’re saying,” he insisted, prying his way out of his hands.

“I do.”  
  
“No…” Dean took a shuddered breath. “I-I need to go.”

And that was that. In the blink of an eye, Dean was gone from that seedy little motel room, leaving Castiel to pine alone, clutching the area of the bed where Dean once had been. 


End file.
